Exemplary embodiments pertain generally to the art of liquid dispensing and to the art of heat exchangers and, more particularly, to the distribution of liquid over the tube banks of an evaporator of a refrigeration chiller.
Refrigeration chillers are commonly used for chilling a working fluid, such as water, to be supplied to heat exchangers associated with a climate-controlled space of a building for conditioning air drawn for the climate-controlled space and passed in heat exchange relationship with the chilled working fluid thereby cooling the air. Refrigeration chillers include a refrigerant vapor compressor, a refrigerant vapor condenser, a refrigerant liquid evaporator, and a refrigerant flow metering device. Depending upon the refrigerant employed, the chiller may be characterized as a high-pressure refrigerant chiller, a medium-pressure refrigerant chiller, or a low-pressure refrigerant chiller.
In the evaporator, which typically is a shell and tube heat exchanger, the working fluid to be chilled is circulated through a plurality of heat exchange tubes arrayed in one or more tube bundles. The refrigerant liquid to be evaporated is fed into the interior of the shell of the evaporator and brought in heat exchange relationship with the refrigerant passing through the heat exchange tubes arrayed in the one or more tube bundles, whereby the liquid refrigerant is evaporated and the working fluid chilled. The working fluid passing from the evaporator is circulated back through the heat exchangers associated with the climate-controlled space. The refrigerant vapor formed in the evaporator circulates back to the compressor to be compressed to a higher pressure, higher temperature vapor state, then passed through the condenser to be condensed back to a liquid state, thence expanded to a lower pressure in passing through the refrigerant flow metering device and fed back into the interior of the evaporator shell.
Typically, in medium and high-pressure falling-film refrigerant chillers, the liquid refrigerant fed to the evaporator is forced through a plurality of spray nozzles to be distributed over the tube bundles. The spray nozzles are arrayed and the nozzle spray patterns designed such that even liquid distribution is achieved over the length of the tube bundles. The use of such spray nozzles entails a non-negligible pressure drop in refrigerant pressure. In medium and high-pressure refrigerant chillers, the resultant pressure drop is not a significant problem due to the relatively large difference between the condensing and evaporating pressures associated with the medium and high-pressure refrigerants. However, in low-pressure refrigerant chiller systems, the high pressure drop attendant with the use of such spray nozzles can be prohibitive due to the inherently low difference between the condensing and evaporating temperatures associated with low-pressure.